Pressure swing gas separators include a bed of adsorbent material which preferentially adsorbs at least one gas from a mixture of gases A pressure swing gas separator uses this preferential adsorption to preferentially remove that gas from a mixture of gases either to provide a gas mixture having a higher concentration of the preferentially adsorbed gas or a depleted gas mixture which has a lower concentration of the preferentially adsorbed gas. In such pressure swing gas separators the adsorbent bed is pressurized with the gas mixture and the preferentially adsorbed component is adsorbed onto the bed until the bed is saturated with that one component of the gas mixture. The bed is then vented and the gas mixture depleted by the preferentially adsorbed component is discharged. The bed is then subjected to a reduced pressure and under these circumstances the gas adsorbed onto the bed is desorbed to produce a gas which is rich in the gas which is preferentially adsorbed.